A number of implantable medical devices have been developed to deliver a variety of medical therapies through a medical lead. Typically, the distal end of the medical lead is implanted adjacent to a therapy site and a separately implanted medical device delivers the therapeutic agent to the therapy site via the medical lead.
In spinal cord stimulation (SCS) systems, a pulse generator is typically implanted within a subcutaneous pocket within the patient. An electrical lead is also implanted within the patient. The proximal end of the electrical lead is electrically coupled (either directly or via one or more extensions) to the pulse generator to receive electrical pulses from the pulse generator. The distal end of the electrical lead is positioned with electrodes of the lead disposed within the epidural space of the patient to deliver the electrical pulses to the spinal neural tissue of the patient. The efficacy of the electrical stimulation in treating chronic pain of the patient depends upon applying the electrical pulses to the appropriate neural tissue. Accordingly, it is desired to retain the stimulation lead at a relatively fixed position over time. An “anchor” structure is frequently sutured to tissue of the patient at a suitable site where the anchor further grips the stimulation lead to prevent migration or movement of the lead from the desired implant location.
Drug infusion implantable systems similarly employ catheters to allow various medical agents to be controllably infused after implantation of the respective system within a patient. For example, implantable medical systems are used or have been proposed for the infusion of insulin, opiates, anti-spasmodic drugs, intrahepatic chemotherapy agents, and other therapeutic agents in a number of countries subject to the regulatory requirements of those countries.
Implantable infusion systems typically include a central housing that includes a reservoir to hold the infusate, a septum to allow infusate to be introduced into the reservoir, an energy source to drive the infusate from the reservoir and through an outlet port, and various flow control elements. The central housing portion of the device is typically implanted in a suitable subcutaneous region with the septum positioned immediately below the skin of the patient to facilitate access to the reservoir for refilling purposes. To deliver the infusate from the reservoir, a catheter is usually attached to the outlet port of the central housing to receive the infusate outflow. The distal end of the catheter is implanted within the patient adjacent to the appropriate therapy site (e.g., at a suitable intrathecal location to allow introduction of an infusate directly into the spinal fluid of the patient). Anchor structures may also be employed to prevent migration of the infusion catheter so that infusate will continue to be delivered to the appropriate therapy site.